Freq reads the given files (default standard input) and prints
histograms of the character frequencies. By default, freq counts
each byte as a character; under the –r option it instead counts
UTF sequences, that is, runes.

Each non–zero entry of the table is printed preceded by the byte
value, in decimal, octal, hex, and Unicode character (if printable).
If any options are given, the –d, –x, –o, –c flags specify a subset
of value formats: decimal, hex, octal, and character, respectively.